Schiff - Radiative properties of soft particles

The Schiff program computes the radiative properties of soft
particles. It uses the Monte-Carlo method to solve Maxwell's equations
within the L. Schiff's
approximation as presented in Charon
et al. 2015.The main advantages of using Monte-Carlo are: the possibility
to address any shape of particle, and the results are provided with a
numerical accuracy.

For a mixture of soft particles, Schiff estimates the total
cross-sections (absorption, scattering and extinction cross-sections) in
addition of the phase function, its cumulative and its inverse
cumulative.

The set of particles to simulate is defined by its refractive index -
provided at various wavelengths - and a geometry distribution that
controls how the particles look like into the mixture. More precisely, this
distribution describes the main shapes of the particles (sphere, cylinder,
helical pipe, etc.) and their statistical variation according to the
distribution of their parameters (gaussian, lognormal, etc.).

A straight interface

Examples of particle shapes handled by Schiff.

The Schiff program is a command-line tool that processes input data,
performs computations, write results and that's all. It makes no assumptions on
how the input data are created excepted that it has to follow the expected file
formats. The simulation results are also provided as is, in a raw ASCII
format.

This thin interface is particularly
well suited to be extended and integrated into any toolchain.
According to the user needs, the optical properties of the particles can be
entered manually or generated by an external program. In the same way, the
output data can either be directly interpreted or post-processed by any script
with respect to the targeted toolchain.

Quick start

Download the desired archive of Schiff and verify its integrity against its
PGP signature. Then extract it. Finally
source the provided schiff.profile file to register the Schiff
installation for the current shell priorly to the invocation of the
schiff program.

$ source ~/Schiff-0.3.1-GNU-Linux64/etc/schiff.profile
$ schiff -h

The Schiff reference documentation is provided trough man pages.
Use the man command-line to consult it.

$ man schiff
$ man schiff-geometry
$ man schiff-output

Post-Process

The following Bash script illustrates how to post-process the Schiff
results. It is an example, provided as is, without additional support.
According to your needs, you can study, modify, extend or redistribute it
freely.

The first generated file, named xsections.txt, lists for each
wavelength submitted with the -w option, its associated
absorption, extinction and scattering cross sections. The second file,
descs.txt, gives overall informations for each simulated
wavelengths, like the limit scattering angles from which its phase function was
analytically computed. Then for each wavelength, the script generates 3 files
named func_<WLEN>.txt, cumul_<WLEN>.txt,
and invcumul_<WLEN>.txt that store for the wavelength
<WLEN>, the value of its associated phase function as well
as its cumulative and its inverse cumulative, respectively.

License

Schiff is free software release under the GPLv3+ license: GNU GPL version 3
or later. You can freely study, modify or extend it. You are also welcome to
redistribute it under certain conditions; refer to the license for details.